Investigators Link Levee Failures to Design Flaws
Monday, October 24, 2005
NEW ORLEANS -- Within a space of 15 hours on Aug. 29, three massive, concrete floodwalls in separate parts of the city suddenly fractured and burst under the weight of surging waters from Hurricane Katrina. The breaches unleashed a wall of water that swept entire buildings from their foundations and transformed what might have been a routine hurricane into the costliest storm in U.S. history.
Today, exactly eight weeks after the storm, all three breaches are looking less like acts of God and more like failures of engineering that could have been anticipated and very likely prevented.
Investigators in recent days have assembled evidence implicating design flaws in the failures of two floodwalls near Lake Pontchartrain that collapsed when weakened soils beneath them became saturated and began to slide. They also have confirmed that a little-used navigation canal helped amplify and intensify Katrina's initial surge, contributing to a third floodwall collapse on the east side of town. The walls and navigation canal were built by the U.S. Army Corps of Engineers, the agency responsible for defending the city against hurricane-related flooding.
The preliminary findings -- based on physical evidence, Corps documents and hydrodynamic models run through a Louisiana State University supercomputer -- are the work of three teams of engineers and forensic experts conducting separate probes. The investigations are shedding light not only on the cause of the failures but also the scale of the rebuilding effort: The discovery of major flaws in the design of the city's levees and floodwalls could add billions of dollars to the cost of New Orleans' recovery.
Investigators already have rejected the initial explanation offered by Corps officials in the hurricane's aftermath that massive storm surges had overtopped and overwhelmed floodwalls on the 17th Street and London Avenue canals on the north side of town. The new findings for the first time point to a human role in all three of the major floodwall failures that left about 100,000 homes underwater and caused most of Louisiana's approximately 1,000 hurricane deaths.
Experts now believe that Katrina was no stronger than a Category 3 storm when it roared into New Orleans, and Congress had directed the Corps to protect the city from just such a hurricane.
"This was not the Big One -- not even close," said Hassan Mashriqui, a storm surge expert at LSU's Hurricane Center. He said that Katrina would have caused some modest flooding and wind damage regardless, but that human errors turned "a problem into a catastrophe."
The National Science Foundation, the American Society of Civil Engineers, and the state of Louisiana are all conducting investigations of the three major floodwall breaches and dozens of smaller ones. Defense Secretary Donald H. Rumsfeld announced last week that the National Academies of science and engineering will lead a separate probe. The Corps has offered data and other assistance to the independent inquiries, but the agency has declined to speculate on the causes of the tragedy.
John Paul Woodley Jr., the assistant Army secretary overseeing the Corps, said it is still too early to cast blame for the drowning of New Orleans. But he said the Corps intends to learn from the Katrina investigations, and use the lessons to build stronger protections for the city.
"I'm not afraid of finding out the truth," Woodley said.
The independent investigations have pointed to two failures in the infrastructure maintained by the Army Corps of Engineers that were critical factors in the destruction Katrina wrought in New Orleans.
In 1965, the Corps completed the 76-mile-long, 36-foot-deep Mississippi River Gulf Outlet, a larger dirt-moving project than the Panama Canal. The outlet -- known locally as MRGO, or "Mr. Go" -- created a navigation shortcut to the Port of New Orleans, although a little-used one that averages fewer than one ship a day. But the outlet also amounted to a funnel that would accelerate and enlarge any storm surges headed for the city's levees.